The technology of the present disclosure relates to a fixing device having a nip pressure adjustment mechanism for adjusting the nip pressure of a nip portion formed by press-contact between a fixing member such as a fixing roller and a fixing belt and a pressure member such as a pressure roller, and an image forming apparatus including the same.
There is a case in which a fixing device includes a nip pressure adjustment mechanism. The nip pressure adjustment mechanism, for example, adjusts the nip pressure of a nip portion in order to prevent wrinkles at the time of paper passing of an envelope and the like or to prevent concaved permanent strain (a so-called C set phenomenon) occurring when a fixing roller has been left in a press-contact state for a long time.
The nip pressure adjustment mechanism inverts an eccentric cam by 180° by a motor via a driving gear train, thereby switching the position of a minimum radius part and the position of a maximum radius part. In this way, the nip pressure adjustment mechanism increases and decreases spring pressure of a compression spring that presses a pressure roller to the fixing roller, thereby adjusting the pressure of a nip portion.